In the East Boston tunnel, a conveyor carries the clay and other material from the shield on January 14, 1932. The shield was a round device of steel about 15 feet long and a little more than 31 feet in diameter. In the front part of the shield the actual work of excavation was done. As fast as the clay was removed, the shield advanced  This big conveyor consisted of a wide belt running over rollers. Along the conveyor ran a steady stream of clay which the muckers burrowed out. The conveyor belt dropped the clay into a huge elevator consisting of a chain of wide buckets. The elevator then carried the clay to the surface where it dropped into waiting trucks and was taken to fill the space around the then East Boston Airport.